Process for making waterproof straw pulpboard



; E. B. WESTON ET AL PROCESS .'FOR MAKING WATERPROOF STRAW PULP BOARD Filed Nov. 4, 1926 I lNV TOR6 '4 [aw/120 52 5570 d WILL/47M a Patented Jan. I, 1929.

EDWARD B. WESTON, F DAYTON, OHIO, AND WILLIAM- INDIANA, ASSIGNORS TO THE TERRE HAUTE PAPER INDIANA, CORPORATION OHIO.

G. GLARK, 0F TERRE HAU'IE,

rnocnss non aAKINs WATERPROOF m ruLrBoARn.

Application filed November 4, 1926. Serial No. 146,153.

This invention is an improvement in straw board, and processes of making the same, and more particularly in moisture resistant straw board, especially adapted for use in the manufacture of fibre packing and shipping containers, and wherein the strawboard sheets are corrugated and usually combined with attached facing and backing sheets.

Straw board is usually made by steam cooking straw with a suitable alkali, such as lime, in a digester.- The straw pulp as usually manufactured has an inherent tendency tofoam in the paper making machine, and this tendency we have discovered is very greatly increased by the addition of sizing, such for instance as rosin or colophony.

Heretofore, it has been impracticable, if not impossible, to make moisture resistant 0 straw board, because, as we finally discovered, of the reaction between the alkali re maining in the pulp after the usual washing and the sizing used in the water proofing process The pulp tends to foam and become slimy, so that it will not cling or stick to the cylinder of-the paper machine.

' We have discovered that by cooking in a properly conducted manner and by eliminating all or substantially all of'the alkali by careful and extended washing, this tendency of the pulp to foam and to become "slimy may be very greatly lessened, and that by reducing'the agitation of the flowing pulp to a minimum, an excellent quality of moisture resistant straw board may be made. onv the usual paper making machine. That isby cooking in the manner to be later described,

afterwards washing' thoroughly, and making the flow of the pulp to the cylinder even so that the. pulp does not become slimy, and readily adheres to the cylinder.

One of the primary objects of the present invention'is the provision of a process for producing a water resistant straw board, wherein the water resistant substance is intimately incorporated with the material of the'board while in the state of pulp, so that 'the board is throughout'uniformly moisture resistant, at the same time sufliciently flexand uniform, thefoaming may be eliminated,

ible 'or pliable to withstand the action of the usual corrugating rolls when the sheets are vto be corrugated. Another object is the provision as an article of manufacture, of a water resistant straw board. I

With these and other objects in View, the

I invention consists in the article and-process" of making the same, it being understood that the ingredients and nature thereof, as Well. as the proportions may be varied within the scope of the claims appended hereto.

In the drawings forming a part hereof, is shown a diagrammatical sectional 'view of a part of a paper making machine of the cylinder type, adapted for the making of the improved board. I

In the usual process of making ordinary straw board, the straw is cooked in digesters with an alkali, such as lime, bymean s of steam. In the present process the same pro-. cedure is followed, exceptthat the cooking COMPANY, or TERRE mum,

operation extends over a definite time, with a definite steam pressure, and with a definite quantity of lime. The cooking, which re:

quires about 145 lbs. of lime to a ton of straw, is continued about ten hours, under about 30 lbs. steam pressure, and the operation isvery c'arefullywatched to'attain precisely the quality. of pulp desired. After cooking, the pulp is subjected to an extended washing operation with clear water, until all or substantially all of the lime is removed. The washing operation is continued until little or no reaction is obtained with the phenylphthalein test. When this result is obtained, the sizing is added to the pulp, and thoroughly incorporated there- I with. W

A preferred sizing material is rosin or colophony and alum. In incorporating the sizing material with the pulp, the rosin is first added to the washed pulp in the beater and thoroughly mixed by the operationof thebeater. The mordant, in the presentinstance alum, is then added, and the opera- ,tion ofthe beater is continued until a complete mixture is obtained. The proportions of rosin and alum will depend somewhat on conditions, such as for instance the character of the water. A suitable proportion is about 90 lbs. of rosin, and 200 lbs. of alum to a ton of pulp. i

We have discovered that the substantial elimination of lime from the pulp greatlyreduces foaming, but some foaming takes place in the paper makingmachine. This we have also discovered is due to the agitation of the pulp, and the foaming is substantially all eliminated by reducing the agitation to a minimum. This" end is attained by making the passage for the flowing pulp wider than usual and of substantially uniform cross sect-ion or capacity throughout. In particular, any restriction at the outletof the passage is avoided.

Straw board,'that is board made from straw pulp, is usually made on a machine of the cylinder type, including a suitable tank or vat 1, and a web forming cylinder 2. The

pulp flows from the stock pipe 3 into the bottom of the tank at one end thereof, and past a series of battles 4, ,5 and 6 to the cylinder.

Referring to the drawing, it will be seen that the battles 4 and 6 extend to the bottom of the tank, while the baffle 5 depends from the top. This arrangement provides a tortuous passage from the stock pipe to the cylinder, the pulp flowing as indicated by the arrows In the usual practice, the baffle 6 is spaced about two inches from the periphery of the cylinder, and all of the bafiles are relatively close, so that a considerable degree ofagitation is imparted to the pulp during the flow from the stock pipe to the cylinder. In the present method the agitation is greatly. lessened and substantially eliminated, by spacing the bafile 6 at least double the usual distance from the cylinder. That is, the distance is increased to at least four inches, and in addition the baflles 4, 5 and 6 are spaced further apart from each other than usual, and from the end of the tank, for a like reason.

Thebaffles 4, 5 and 6 are spaced apart ect ually from each other and from the end 0 the tank, and the opening between each baflle and the tank wall is of the same cross I flow 0 the pulp is uniform and with a mini 1 section as the space between adjacent battles. The excess of waste water is drawn out through a suction pipe 7 on the inner side of the baflle 6.

This arrangement provides a passage for the pulp of.\substantially uniform capacity from, the stock pipe to the cylinder, and without an restriction at the outlet, so that the mum of agitation at the entrance to the body of the tank, that is between the baffle 6 and the cylinder.

So far as we are aware, we are the first to produce a moisture resistant article of 'the character in question from straw pulp steam digested in the presence of an alkali,

and particularly wherein the moisture resistant material or size is intimately incorporated with the thoroughly washed pulp fibres during the beating, so that every part of the article is permeated by the size. -We are able to produce this article, by the care exercised in the cooking of the pulp, in the elimination of the alkali, and in the substantial elimination of agitation in the flow of the pulp to the web forming cylinder, so that. the pulp is devoid of sliminess, and will be picked up by the cylinder. The rosin referred to as in the proportion of 90 lbs. to the ton of stock is the usualprepared rosin size, but the proportion of rosin and the addition of a mordant, such as alum, in about the proportion stated, is we believe, new with us as applied in the manufacture of pulp prepared in the manner and for the purposes herein described.

What is claimed as new is:

1. As a new product of manufacture, water and moisture repellent pulp board formed from straw fibres substantially free from alkali and having a rosin size incorporated therein.

2. As a new productof manufacture, water and moisture repellent pulp boa-rd formed from steam digested straw fibres substantially free from alkali and having rosin size and a mordant incorporated therein.

3. As a new product of manufacture, wa-

ter and moisture repellent pulp board formed from steam digested straw fibres substantially free from alkali and having rosin size and a mordant incorporated therein in about the proportions of 90 lbs. of rosin and 200 lbs. of alum to approximately a ton of pulp.

.4. The herein described process of makingwater and moisture repellent strawboard which consists in steam digesting straw in the presence of an alkali, ing the digested straw to form a pulp, then washing the pulp to remove all or substantially all traces of alkali, then thoroughly incorporating rosin size with the alkali cleansed pulp, and then feeding the pulp quietly and without undue agitation to a pulp-making machine and forming the same i into a sheet.

5. The herein described process of making water and moisture repellent strawboard which consists in steam digesting strawin the presence of an alkali, then thoroughly beating the digested straw to form a pulp, then washing the pulp to remove substantially all then thoroughly beat-' beating the digested straw to form a pulp, due agitation to a paper-making machine thenthoroughly washing the pulp to remove and forming the same into a sheet. 10 substantially all traces of ,alkali, 'then thor- Signed at Terre Haute in the county of oughly incorporating rosin size and alum Vigo and State of Indiana this 25th day of ,5 with the lime-cleansedpulp in the propor- October, A. D. 1926'.

tions of about 90 lbs. of rosin and 200 lbs. I of alum to approximately a ton of pulp, and EDWARD B. WESTON. then feeding the pulp quietly and'without un- Y WILLIAM G. CLARK. 

